US10894141B2 - Hyperthermic humidification system - Google Patents

Abstract

Apparatus and methods for delivering humidified breathing gas to a patient are provided. The apparatus includes a humidification system configured to deliver humidified breathing gas to a patient. The humidification system includes a vapor transfer unit and a base unit. The vapor transfer unit includes a liquid passage, a breathing gas passage, and a vapor transfer device positioned to transfer vapor to the breathing gas passage from the liquid passage. The base unit includes a base unit that releasably engages the vapor transfer unit to enable reuse of the base unit and selective disposal of the vapor transfer unit. The liquid passage is not coupled to the base unit for liquid flow therebetween when the vapor transfer unit is received by the base unit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 16/120,923 filed on Sep. 4, 2018, which is a continuation of U.S. patent application Ser. No. 14/547,012 filed on Nov. 18, 2014, now U.S. Pat. No. 10,092,722, which is a continuation of U.S. patent application Ser. No. 11/973,061, filed on Oct. 5, 2007, now U.S. Pat. No. 8,905,023. The specifications of each of the foregoing applications are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to apparatus and methods for respiratory tract therapy. More particularly, this invention relates to an apparatus configured to deliver heated and humidified breathing gas to a patient.

BACKGROUND OF THE INVENTION

Respiratory airway therapies are recognized medical treatments that enhance breathing by delivering breathing gas to the respiratory tract of patients. Respiratory devices such as humidifier/ventilator systems, however, include parts that may be at risk of contamination due to contact with water or water vapor. While disinfection protocols have been developed to minimize and control bacterial growth, there remains a need for an improved apparatus for respiratory tract therapy that can be used in various settings including clinical and hospital settings that reduces the risk of bacterial contamination. There also remains a need for improved methods of respiratory airway therapy.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a humidification system configured to deliver humidified breathing gas to a patient. The humidification system includes a vapor transfer unit and a base unit. The vapor transfer unit includes a liquid passage, a breathing gas passage, and a vapor transfer device positioned to transfer vapor to the breathing gas passage from the liquid passage. The system includes a base unit that releasably engages the vapor transfer unit to enable reuse of the base unit and selective disposal of the vapor transfer unit. The liquid passage is not coupled to the base unit for liquid flow therebetween when the vapor transfer unit is received by the base unit.

In another aspect, the humidification system configured to deliver humidified breathing gas to a patient includes a vapor transfer unit and a base unit. The vapor transfer unit includes a liquid passage, a breathing gas passage, and a vapor transfer device positioned to transfer vapor to the breathing gas passage from the liquid passage. The base unit releasably engages the vapor transfer unit. The base unit has at least one sensor positioned to sense a parameter in the liquid passage of the vapor transfer device.

In yet another aspect, the humidification system configured to deliver humidified breathing gas to a patient includes a vapor transfer unit and a base unit. The vapor transfer unit has a liquid passage and a first pump portion positioned to advance liquid through the liquid passage. The base unit releasably engages with the vapor transfer unit. The base unit has a second pump portion adapted to operationally mate with the first pump portion to advance liquid through the liquid passage of the vapor transfer unit when the base unit engages the vapor transfer unit.

In still another aspect, the humidification system is configured to deliver heated and humidified breathing gas to a patient and includes a vapor transfer unit and a base unit. The vapor transfer unit has a liquid passage and a first heater portion positioned to heat liquid in the liquid passage. The base unit releasably engages the vapor transfer unit to enable reuse of the base unit and selective disposal of the vapor transfer unit. The liquid passage is not coupled to the base unit for liquid flow therebetween when the vapor transfer unit is received by the base unit. The base unit has a second heater portion adapted to conduct heat to the first heater portion to heat liquid in the liquid passage of vapor transfer unit.

In still yet another aspect, the invention provides a vapor transfer unit for use with a base unit of a humidification system for delivering heated and humidified breathing gas to a patient. The vapor transfer unit is configured to be releasably mounted to base unit to accommodate reuse of base unit and selective disposal of vapor transfer unit. The vapor transfer unit includes liquid and breathing gas passages and a vapor transfer device is positioned to transfer vapor to the breathing gas passage from the liquid passage. An impeller is positioned to advance liquid through the liquid passage and a sensor is positioned to sense a level of liquid in the liquid passage.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed description when read in connection with the accompanying drawings, with like elements having the same reference numerals. This emphasizes that according to common practice, the various features of the drawings are not drawn to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:

FIG. 1 is a schematic representation of a humidification system according to an exemplary aspect of this invention;

FIG. 2 is a front perspective view of an exemplary embodiment of the humidification system in accordance with the present invention;

FIG. 3A is a side perspective view of the humidification system shown inFIG. 2, with a vapor transfer cartridge partially inserted into a base unit;

FIG. 3B is a side perspective view of the humidification system shown inFIG. 2, with the vapor transfer cartridge fully inserted into the base unit;

FIG. 4 is rear perspective view of the humidification system shown inFIG. 2;

FIG. 5 is a schematic representation of the humidification system shown inFIGS. 2, 3, and 4 according to aspects of the invention;

FIG. 6A is a perspective view of a first portion of a gas blending device according to an aspect of the invention;

FIG. 6B is an interior view of the first portion of the gas blending device shown inFIG. 6A;

FIG. 6C is an exterior view of the first portion of the gas blending device shown inFIG. 6B;

FIG. 7A is a perspective view of a second portion of the gas blending device configured to mate with the first portion shown inFIG. 6A;

FIG. 7B is an interior view of the second portion of the gas blending device shown inFIG. 7A;

FIG. 7C is an enlarged view of laminar fins shown inFIG. 7B;

FIG. 7D is a cross-sectional view of the laminar fins, taken alonglines7D-7D ofFIG. 7C;

FIG. 7E is an exterior view of the second portion of the gas blending device shown inFIG. 7B;

FIG. 8A is a front perspective view of a chassis of the humidification system;

FIG. 8B is a rear elevation view of the chassis shown inFIG. 8A;

FIG. 8C is an exterior side elevation view of the chassis shown inFIG. 8A;

FIG. 8D is an interior side elevation view of the chassis shown inFIG. 8C;

FIG. 8E is a cross-sectional view of the chassis, taken along lines8E-8E ofFIG. 8D;

FIG. 8F is a top view of the chassis shown inFIG. 8A;

FIG. 8G is a top perspective view of an exemplary base unit that may be used with an embodiment of a humidification system according to the present invention;

FIG. 9 is a perspective view of a pump portion the humidification system according to an aspect of the invention;

FIG. 10A is front perspective view of a fluid pathway module of the humidification system shown inFIG. 3;

FIG. 10B is rear perspective view of the fluid pathway module shown inFIG. 10A;

FIG. 11A is an exploded view of the fluid pathway module shown inFIGS. 10A and 10B;

FIG. 11B is another exploded view of the fluid pathway module shown inFIGS. 10A and 10B;

FIG. 12 is an exploded view of the fluid pathway module shown inFIG. 11B;

FIG. 13 is a front elevation view of the humidification system according to aspects of the invention; and

FIG. 14 is a flowchart showing operation of an exemplary embodiment of a humidification system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the invention will now be described with reference to the figures. Such figures are intended to be illustrative rather than limiting and are included herewith to facilitate the explanation of the present invention.

Humidification System

Referring generally to the figures (FIGS. 1-14), in accordance with an exemplary embodiment, the invention provides ahumidification system100 to deliver heated and humidifiedbreathing gas80 to a patient.Humidification system100 includes abase unit110 and a vapor transfer unit, or fluid pathway module,120.Base unit110 may include controls for operatinghumidification system100 and is configured to operate without liquid flowing throughbase unit110 or being exchanged withfluid pathway module120.Fluid pathway module120 is releasably mounted tobase unit110 and is configured to operate withliquid70, such as water, flowing through fluid pathway module120 (but not base unit110) to allow reuse ofbase unit110 and selective disposal offluid pathway module120. Thus, cost savings and lowered contamination risk forhumidification system100 can be realized through reuse ofbase unit110 and by periodically changing fluid pathway module (e.g., for each patient and/or at a determined time interval), which is the component that contacts the water and water vapor, and therefore more prone to bacterial contamination.

Referring now to the individual figures in detail,FIG. 1 illustrates a schematic representation ofhumidification system100.Humidification system100 manages the delivery of heated and humidifiedbreathing gas80 to the patient and includesbase unit110 andfluid pathway module120. The illustratedbase unit110 includes the controls for operatinghumidification system100 and is configured to receivebreathing gas50a,50b, such as medical air and oxygen, respectively. Alternatively, the controls may be remote tobase unit110. In addition, other gases, such as, for example, helium, nitric oxide (INO), carbon dioxide, and/or other gases, may be used. For gases other than air and oxygen,base unit110 may need to be recalibrated for the specific gases being used. When different types of gas are received throughbase unit110,gases50a,50bmay be blended bygas blending device84, to form blendedgas60, which is delivered tofluid pathway module120. While two different gases may be used withsystem100, those skilled in the art will recognize thatsystem100 may be used with only one gas, such as, for example pure oxygen or air, in which casegas blending device84 may be omitted.

Fluid pathway module120 is releasably mounted tobase unit110 and is configured to receivegas60 frombase unit110 and liquid70 from an external water source. In an exemplary embodiment, liquid70 received byfluid pathway module120 is contained in areservoir32 to minimize potential contamination ofbase unit110 and to prime a pump used to circulateliquid70.Liquid70 contained inreservoir32 may be heated byheat conduction62 frombase unit110.Vapor transfer device99 releasably mounted tofluid pathway module120 combines liquid70 fromreservoir32 and blendedgas60 to supply heated and humidifiedbreathing gas80 to a patient.

Base Unit

Referring now toFIGS. 2, 3A, 3B, and 4, an exemplary embodiment ofhumidification system100 according to the present invention is illustrated.Humidification system100 includesbase unit110, which contains the controls that operatehumidification system100 and is configured to operate without liquid flowing internally throughbase unit110 or being exchanged withfluid pathway module120. In the exemplary embodiment,base unit110 is completely dry so that potential damage to electronics that controlhumidification system100 and bacterial contamination ofbase unit110 is minimized.

Base unit110 is mountable to astand90, such as an IV pole, via mountingmechanism95, shown inFIG. 4. In an exemplary embodiment,rear panel102 ofbase unit110 includes a bracket95band aknob95athat manipulates bracket95bto releasablysecure base unit110 to stand90. Whenknob95ais rotated, for example, bracket95bmay be tightened or loosened onstand90, thereby securing or looseninghumidification system100 with respect to stand90.

The rear ofbase unit110, best illustrated inFIG. 4, further includes gas inlet ports withfilters101a,101bthat are configured to connect to gas supply lines (not shown). The gas supply lines supply gas (such as medical air and oxygen) from a portable tank, compressor, or wall outlet intobase unit110. In an exemplary embodiment, gas supplied tobase unit110 may be filtered and blended to provide a contaminant-free gas mixture. A gas blending device (not shown inFIGS. 2-4), for example, may be installed withinbase unit110 to blend the gas being supplied intobase unit110. Additional aspects of the gas blending device and gas blending operation will be described in further detail below.

The side ofbase unit110, best illustrated inFIGS. 2-4, includes adoor103 that may be slid open or closed to expose or cover acomponent receiving portion119 ofbase unit110. As shown inFIGS. 2 and 4,door103 may be slid completely closed to cover thecomponent receiving portion119 from view. As illustrated inFIGS. 3A and 3B,door103 is slid open to exposecomponent receiving portion119 ofbase unit110. Whendoor103 is open,fluid pathway module120 can be releasably mounted or removed fromcomponent receiving portion119, e.g., using ahandle121. Aguide144 extends from the side ofcomponent receiving portion119 to align and securefluid pathway module120 tobase unit110.FIG. 3A showsfluid pathway module120 partially installed onbase unit110 andFIG. 3B showsfluid pathway module120 fully installed onbase unit110.

In an exemplary embodiment, whenfluid pathway module120 is mounted tobase unit110,fluid pathway module120 is positioned to receive gas frombase unit110. A gas outlet (not shown inFIGS. 2-4) ofbase unit110 engages a gas inlet (not shown inFIGS. 2-4) offluid pathway module120 to form an airtight channel through which gas, received throughinlet port101a, may be transferred tofluid pathway module120. As shown inFIGS. 2-4,fluid pathway module120 is also configured to receive liquid from aliquid supply line75 vialiquid inlet124. Liquid may be supplied tofluid pathway module120, for example, via a sterile water bag (not shown) that is suspended abovehumidification system100. The sterile water bag may be punctured by a tube spike (not shown), with water being gravity fed from the water bag intofluid pathway module120 vialiquid supply line75. An exemplary tube spike is disclosed in U.S. patent application Ser. No. 10/918,515 owned by the Assignee of the present invention, which is incorporated herein in its entirety by reference. In an exemplary embodiment, liquid is stored within reservoir32 (shown schematically inFIG. 1) influid pathway module120 that is provided to receive humidification fluid from the water bag as well as recirculated humidification fluid. The circulated humidification fluid/liquid influid pathway module120 liquid does not flow throughbase unit110. Liquid contained influid pathway module120 is vaporised invapor transfer device99 and combined with gas frombase unit110 to generate humidified breathing gas. As shown inFIG. 3A, adelivery tube85 is releasably coupled to abreathing gas outlet125 offluid pathway module120 to deliver humidified breathing gas to the patient.

As illustrated inFIG. 4,rear panel102 ofbase unit110 includes apressure relief valve91 that vents excess gas frombase unit110 if gas pressure supplied tobase unit110 fromgas inlet ports101a,101bis too high.Base unit110 also includes a service access cover92 which is coupled to therear panel102 ofbase unit110. Service access cover92 may be removed frombase unit110 to provide access to internal components withinbase unit110.

As shown inFIG. 4, anelectrical cord65 is coupled tobase unit110 topower humidification system100. Whenelectrical cord65 is removed or AC power is temporarily unavailable, an internal battery (not shown) withinbase unit110 may provide DC power tohumidification system100.Humidification system100 may operate on DC power, for instance, when a patient is being transported from one location to another or during power interruptions, thus providinghumidification system100 portability and continued operations. In order to conserve battery power, the heater (not shown) that heats the fluid influid pathway module120 does not operate in battery mode.

As further illustrated inFIG. 2,humidification system100 has afront panel104 that includes adisplay panel105, such as a liquid crystal display (LCD) or light emitting diode (LED) display that provides visual indication of user settings and status conditions ofhumidification system100. In an exemplary embodiment, the user settings may include user adjustable settings such astemperature106a,flow rate106b, andoxygen saturation level106cof the breathing gas to be delivered to the patient. User settings may be adjusted, for example, viauser interface107.User interface107 includesbuttons108a,108b,LEDs109a,109b, andknob111 to adjust and monitor operating conditions ofhumidification system100. Additional aspects of thedisplay panel105 anduser interface107 will be described in further detail below according to aspects ofhumidification system100 operation.

Referring now toFIG. 5, a detailed schematic diagram ofhumidification system100 showing gas and fluid flow paths is illustrated. Schematic representations ofbase unit110,fluid pathway module120, andvapor transfer device99 are shown.Fluid pathway module120 is configured to be releasably mounted tobase unit110, andvapor transfer device99 is configured to be releasably mounted tofluid pathway module120.

Base unit110 includes controls for operation ofhumidification system100 and has inlet ports configured to receivegas50a,50b, such as medical air and oxygen. Gas input intobase unit110 is controlled by two proportional solenoids PSOL1, PSOL2 that regulate the flow ofgas50a,50b, respectively, intobase unit110. Proportional solenoids PSOL1, PSOL2, respectively, to regulate gas input flow intobase unit110. Gas pressure sensors PS1, PS2 monitor gas pressure upstream of solenoids PSOL1, PSOL2, respectively. Checkvalves51a,51bdirect gas flow intogas blending device84 and prevent reverse flow ofgas50a,50b.

In an exemplary embodiment, gas flow rate ofair50aandoxygen gas50bare monitored by mass flow sensor MFS1, MFS2, respectively, positioned ongas blending device84.Air50aandoxygen gas50bare blended ingas blending device84 and blended gas pressure is monitored by gas pressure sensor PS4. An oxygen sensor OS1 is coupled to a three-way solenoid valve SOL1 and monitors the oxygen saturation level of the blended gas. If the oxygen saturation level of the blended gas is below a user setpoint, proportional solenoid valve PSOL1 feedsadditional oxygen gas50binto the blended gas. Likewise, if oxygen saturation level of the blended gas is above a user setpoint, proportional solenoid valve PSOL1 reduces the amount ofoxygen gas50binto the blended gas. Gas pressure sensor PS4 is coupled to a microcontroller (not shown) and monitors the pressure of the blended gas. If the blended gas pressure exceeds a certain safety threshold,humidification system100 emits an audible and a visual alarm. Additionally, when gas pressure sensor PS4 senses a low pressure, gas flow is limited bysystem100.

As shown schematically inFIGS. 1 and 5, blendedgas60 is delivered tovapor transfer device99, which is mounted tofluid pathway module120. Sensors CS1, CS2 positioned within a base unit interface, such ascomponent receiving portion119, shown inFIG. 3, ofbase unit110 detect the presence ofvapor transfer device99 coupled tofluid pathway module120. For example, sensors CS1, CS2 may read a barcode or optically detect an indicator onvapor transfer device99 whenfluid pathway module120 is mounted tobase unit110.

Fluid pathway module120 receives water, e.g. from a water bag33, intoreservoir32. Two water level sensors LS1, LS2 onbase unit110 monitor water level withinreservoir32. For example, water level may be monitored by optical detection, as will be described in further detail below. Whenfluid pathway module120 is mounted tobase unit110, water fromreservoir32 is pumped by a pump portion PMP1 offluid pathway module120. Pump portion PMP1 is operationally coupled to a stator STA1 ofbase unit110 to pump water fromreservoir32 to a heater HTR1. Heater HTR1 receives thermal energy from base unit heater HTR2 to heat water to a user specified temperature. A temperature switch (OVERTEMP SWITCH) controls heater HTR2 onbase unit110 to provide a safety backup to prevent water influid pathway module120 from overheating. Heated water is pumped to a closed double lumen of apatient delivery tube85 that is coupled tofluid pathway module120. Heated water is recycled fromdelivery tube85 intovapor transfer device99. In an exemplary embodiment, heated water is supplied throughpatient delivery tube85 to minimize water condensation of breathinggas80 and to maintain the temperature of breathinggas80 as it makes its way to the patient. Infrared temperature sensors IR1, IR2 monitor the temperature of the water being delivered to and returned fromdelivery tube85 and provide feedback to system controller (not shown) in order to maintain a desired temperature of the breathing gas at the outlet ofdelivery tube85. Additional aspects ofexemplary delivery tube85 andvapor transfer device99 are described in U.S. Patent Application Publication No. 2003/0209246 and U.S. Patent Application Publication No. 2004/0245658, which are incorporated herein fully by reference.

Blended gas frombase unit110 is combined with heated water vapor invapor transfer device99 to generate heated and humidifiedbreathing gas80. The heated and humidifiedbreathing gas80 is delivered to a breathing gas lumen of thepatient delivery tube85. Excess heated water delivered tovapor transfer device99 may be recycled intowater reservoir32. Bubble sensor BS1 monitors air bubbles inreservoir32 and bubble sensor BS2 monitors the presence of water droplets in thebreathing gas80 to determine whenvapor transfer device99 and/orfluid pathway module120 should be replaced. In an exemplary embodiment,fluid pathway module120 has a continuous duty life of about 720 hours and about a 1000 hour test life.

Gas Blending Device

Referring now toFIGS. 6A, 6B, 6C, 7A and 7B,gas blending device84 is illustrated. Reference to these figures also includes references to sensors represented inFIG. 5.Gas blending device84 may be constructed from a first, generally planar portion71 (FIGS. 6A, 6B, 6C) and a second generally planar portion81 (FIGS. 7A, 7B).Planar portions71,81 each include complementary channels such that whenplanar portions71,81 are assembled together, flow passages are formed withingas blending device84. For example,channels73aand83acombine to form a first passage,channels73band83bcombine to form a second passage, andchannels73cand73ccombine to form a third passage.First portion71 is configured to mate withsecond portion81 shown inFIGS. 7A-7B to provide a fully assembledgas blending device84. Whenfirst portion71 is secured to second opposingportion81, edges72a,72boffirst portion71 form an air tight seal withedges82a,82bofsecond portion81 to prevent gas leakage and provide efficient gas blending operation.Gas blending device84 is configured to be installed internally withinbase unit110.

Pilot holes77a-cand pins78a-c, shown inFIGS. 6A-6C, are positioned onfirst portion71 ofgas blending device84 to align and secure thefirst portion71 to the second opposingportion81 shown inFIGS. 7A-7B. In an exemplary embodiment, pilot holes77a-cand pins78a-cprovide additional connection surface area and mechanical strength to thegas blending device84. Pilot holes87a-cand pin inserts88a-care positioned on the body ofsecond portion81 and are configured to mate with pilot holes77a-cand pins78a-cof thefirst portion71.

An interior view of thefirst portion71 ofgas blending device84 is illustrated inFIGS. 6A and 6B.First portion71 ofgas blending device84 includes twochannels73a,73bthat are each configured to receive gas throughinlets74a,74b, respectively.Channels73a,73bdirect gas to blendingchannel73c. Blendingchannel73cleads to mainterminal channel73dwhere blended gas may exit throughsecond portion81 and flow to a gas outlet, shown asgas outlet649 inFIG. 8C, ofbase unit110. Upstream of mainterminal channel73dis apressure relief outlet74cthat functions as a secondary gas exit if gas pressure exceeds a predetermined value. In an exemplary embodiment,pressure relief outlet74cis part of a pressure relief valve system, which may open or close pressure relief valve91 (shown schematically inFIG. 5), depending on gas pressure withingas blending device84.Passage73eprovides for gas flow to oxygen sensor OS1 (shown schematically inFIG. 5).

Referring now toFIGS. 7A and 7B an interior view ofsecond portion81 ofgas blending device84 is shown.Second portion81 ofgas blending device84 is configured to mate with thefirst portion71 shown inFIGS. 6A-6C.Second portion81 includeschannels83a,83bhaving fins66a,66bwithin eachchannel83a,83b.Fins66a,66bpromote laminar flow across mass flow sensors MFS1, MFS2 (shown schematically inFIG. 5) installed throughopenings76a,76bof the first portion71 (FIG. 7B) ofgas blending device84.Walls69a,69bdefinechannel83asuch that when gas blending portion71 (FIG. 6B) mates with the second opposing portion81 (FIG. 7B), air tight channels are formed.

Channels83a,83bdirect gas to a blendingchannel83cthat includes atortuous path67 to efficiently mix gas together prior to reachingterminal channel83d.Channel83emates withchannel73eto form a passage to oxygen sensor OS1 (shown schematically inFIG. 5).

In an exemplary embodiment, gas metering operation ofhumidification system100 determines the precise flow rate of gas within eachchannel73a,83ato obtain a blended gas mixture having an oxygen saturation level between 21% and 100% O₂. Oxygen saturation level of blendedgas mixture60 shown inFIG. 1 may be monitored by oxygen sensor OS1, which is shown inFIG. 5.

As shown inFIGS. 6A-6C,first portion71 ofgas blending device84 includessensor openings76a,76bwhich open into either end of passage76c. Passage76cis in fluid communication with mass flow sensor MFS1 (not shown inFIGS. 6A-6C), which monitors gas flow rate in channel73ato control the gas metering operation ofhumidification system100.FIG. 6C illustrates an exterior view offirst portion71 ofgas blending device84.First portion71 includes threadedinserts79a,79bto mount mass flow sensor MFS1.

As shown inFIG. 7B,channel83bofsecond portion81 includessensor openings86a,86bwhich open into either end of passage86c. Passage86cis in fluid communication with mass flow sensor MFS2 (not shown inFIGS. 7A-7B), which monitors gas flow rate inchannel83ato control the gas metering operation of humidification system109.FIG. 7E illustrates an exterior view ofsecond portion81 ofgas blending device84,Second portion81 includes threadedinserts89a,89bto mount mass flow sensor MFS2 throughopenings86a,86b.Main gas outlet68 provides an exit for blended gas to flow togas outlet649, shown inFIG. 8C, ofbase unit110.

The gas flow rate detected by mass flow sensor MFS1, MFS2 in channel73amay be sent to a microcontroller that controls proportional solenoid valves PSOL1, PSOL2. Proportional solenoid valve PSOL1 or PSOL2 may vary gas input flow in channel73aby increasing or decreasing gas flow through theinlet74a. Thus, an adequate ratio of gas flow may be supplied to channel73ato obtain a desired blended oxygen saturation level. In an exemplary embodiment, oxygen sensor OS1, which may be positioned in oxygen sensor opening744, is calibrated to 100% O₂during a system power up sequence. Once calibrated, the oxygen sensor OS1 measures oxygen content of blended gas to ensure that blended gas is within 98% to 102% of a selected oxygen percentage setpoint. If detected oxygen content falls below 98% of the selected oxygen level, the microcontroller may adjust proportional solenoid valves PSOL1, PSOL2 to increase the flow ofoxygen gas50band/or decrease the flow ofair50a. Alternatively, if detected oxygen content is above 102% of the selected oxygen level, the microcontroller may adjust proportional solenoid valves PSOL1, PSOL2 to decrease the flow ofoxygen gas50band/or increase the flow ofair50athroughinlet74bor74a.

Base Unit Chassis

Referring now toFIGS. 8A-8G, an exemplary embodiment of abase unit chassis640 is illustrated.Base unit chassis640 contains the interfaces withfluid pathway module120. References to these figures also include references to sensors BS1, BS2, electronic readers CS1, CS2, water level sensors LS1, LS2, temperature sensors IR1, IR2, pump stator STA1, and heater HTR2, which are shown schematically inFIG. 5 and with reference tobase unit110 inFIG. 8G. It will be appreciated thatbase unit chassis640 houses the electronic components ofhumidification system100 and is configured such that liquid does not flow internally throughbase unit110.

As shown inFIGS. 2 and 8A,base unit chassis640 includes a front portion640ainto whichdisplay panel105 may be installed. Threaded inserts641a-dare provided on front portion640aofchassis640 to securedisplay panel105 tobase unit chassis640. Whendisplay panel105 is secured,front panel104 may be fitted over afront edge642 ofbase unit chassis640 to prevent access to the electrical connections ofdisplay panel105. After installation offront panel104,slidable door103 as shown inFIG. 3, may be secured tobase unit chassis540 via threadedinserts643a,643blocated on the top and side ofbase unit chassis640.

As shown inFIGS. 3A, 3B, and 8A,base unit chassis640 includes acomponent receiving portion619 configured to receivefluid pathway module120. A guide644aextends along the side of thecomponent receiving portion619 to align and securefluid pathway module120 tobase unit100.Base unit chassis640 has aseat645 to supportfluid pathway module120 and aseat opening646 in which a pump portion such as stator STA1 may be installed via threaded inserts647a-c. Whenfluid pathway module120 is seated incomponent receiving portion619, stator STA1 (shown schematically inFIG. 5) ofbase unit110 operationally mates with pump portion PMP1 (shown schematically inFIG. 5) offluid pathway module120. In an exemplary embodiment, stator STA1 may drive pump portion PMP1 which may be an impeller that is magnetically driven by stator STA1 to advance liquid through a liquid passage offluid pathway module120. An exemplary embodiment of a pump having a separate pump portion PMP1 and a separate stator portion STA1 is manufactured by Laing Thermotech. Inc., located in Chula Vista, Calif. In yet another embodiment (not shown), the entire pump portion may be provided only onbase unit110 to provide a low cost, disposablefluid pathway module120. Alternatively, the entire pump portion may be provided only onfluid pathway module120

Base unit chassis640 includes a recessedportion648 that has agas outlet649. Whenfluid pathway module120 is inserted onbase unit110, recessedportion648 aligns with and supports agas receiving portion130, shown inFIG. 10B, offluid pathway module120. The gas receiving portion offluid pathway module120 includes a gas inlet which is configured to couple to thegas outlet649 ofbase unit110 to provide an air tight seal through which gas may be transferred frombase unit110 to the gas passage offluid pathway module120.

Thecomponent receiving portion619 ofbase unit chassis640 has arectangular opening651 into which heater HTR2, shown inFIG. 5, such as a heat conduction plate may be installed. Whenfluid pathway module120 is releasably mounted tobase unit110, heater HTR2 ofbase unit110 contacts heater HTR1,FIG. 5, offluid pathway module120,FIG. 3. Heater HTR1 offluid pathway module120 may also be a heat conduction plate HTR2 such that when electrical current is supplied to the heat conduction plate ofbase unit110, energy is transferred to heat conduction plate HTR1 offluid pathway module120. Thermal energy received by heat conduction plate HTR1 offluid pathway module120 is used to heat the liquid contained withinfluid pathway module120 for delivery to the patient at a temperature specified by the user. In an exemplary embodiment, the user may adjust the temperature setting of humidification system in 1° C. steps to a maximum temperature of 43° C. and a minimum temperature of 33° C. A temperature sensor opening652ainbase unit chassis640 is configured to receive temperature sensor IR1 to monitor the temperature of the liquid that is supplied todelivery tube85.

Base unit chassis640 also includes a bubble sensor opening653aadjacent temperature sensor opening652a. Bubble sensor opening653ais configured to receive bubble sensor BS1 that monitors the formation of air bubbles inliquid reservoir32 of fluid pathway module. Additional aspects of bubble sensor BS1 will be described in further detail below.

Referring toFIGS. 5 and 8A, two waterlevel sensor openings654a,654bare positioned onbase unit chassis640. Waterlevel sensor openings654a,654bare each configured to receive a water level sensor LS1, LS2 to monitor the water level withinliquid reservoir32 offluid pathway module120. In an exemplary embodiment, optical water level sensors LS1, LS2 are aimed atreflectors128a,128b, shown inFIG. 10A, located at the top and bottom ofliquid reservoir32 to determine when theliquid reservoir32 is full, low, or empty. Additional aspects of water level sensors LS1, LS2, shown inFIG. 5, will be described in further detail below.

FIG. 8B illustrates a rear view ofbase unit chassis640 in which water level sensors LS1, LS2 may be installed. As described above, waterlevel sensor openings654a,654bare each configured to receive a water level sensor LS1, LS2, respectively. Water level sensors LS1, LS2 may be mounted tobase unit chassis640 via threaded inserts655a-d.Rear panel102, shown inFIG. 4, may be fitted overrear edge656 ofbase unit chassis640 to restrict access to the electrical connections of water level sensors LS1, LS2.

FIG. 8C illustrates a side view ofbase unit chassis640 in whichfluid pathway module120, shown inFIG. 3, may be releasably mounted. An electronic reader opening657 onbase unit chassis640 is configured to receive electronic reader CS1, CS2 that detects the type ofvapor transfer device99 coupled tofluid pathway module120.Vapor transfer device99 may be, for example, a disposable, cartridge that is labeled with anindicator194 such as a sticker or barcode. In an exemplary embodiment, a high flowvapor transfer device99 is labeled with an all-reflective sticker while a low flowvapor transfer device99 is labeled with a portion reflective/portion non-reflective sticker. Electronic reader CS1, CS2 may monitor the optical properties of the sticker to identify the type ofvapor transfer device99 installed inhumidification system100. Whenindicator194 is read by electronic reader CS1, CS2, a signal is sent to a microprocessor (not shown) to control the gas metering operation ofhumidification system100. For example, when a low flow ratevapor transfer device99 is installed, the microcontroller may limit the flow rate of the breathing gas being delivered to a setpoint between 0.5 LPM (liters per minute) and 8 LPM. If a high flow ratevapor transfer device99 is installed, the microcontroller may limit the flow rate between 8 LPM and 40 LPM. In an exemplary embodiment, when a user attempts to adjust the flow rate setpoint beyond the limits defined by the microcontroller,humidification system100 generates an auditory warning and prevents the setpoint from deviating beyond the maximum and minimum flow rate limits of a high flow or low flowvapor transfer device99.

Referring toFIGS. 5 and 8C, a temperature sensor opening652aofbase unit chassis640 is configured to receive infrared temperature sensor IR1 that detects the temperature of liquid influid pathway module120. A secondtemperature sensor opening652bis configured to receive second infrared temperature sensor IR2 that detects the temperature of liquid returning back tofluid pathway module120 fromdelivery tube85. In an exemplary embodiment, monitoring of the two temperatures allowshumidification system100 to efficiently operate heater HTR2, which is mounted throughheater opening651 ofbase unit chassis640. For example, activation and deactivation of HTR2 may be controlled by a PID (proportional-integral-derivative) feedback controller to maintain a consistent temperature of the breathing gas being delivered to a patient.

Adjacent thetemperature sensor openings652a,652bofbase unit chassis640 arebubble sensor openings653a,653bthat are each configured to receive a bubble sensor BS1, BS2, respectively. During operation of humidification system, air bubbles may be detected inliquid reservoir32 offluid pathway module120 due to air permeating under pressure through the exchange media invapor transfer device99 offluid pathway module120. Under normal operating conditions, the water and gas passages offluid pathway module120 are connected to vapor transfer device where a portion of the liquid is transferred to the gas. Over time, as gas and liquid flow internally through vapor transfer device, the core of vapor transfer device may begin to degrade such that the mixing interface between the gas and liquid passages erodes. As the interface degrades, gas from the gas passage may pass into the liquid passage such that air bubbles begin to form inliquid reservoir32 offluid pathway module120. Conversely, liquid from the liquid passage may pass into the gas passage such that liquid droplets are mixed into the gas flow. Bubble sensors BS1, BS2 that are mounted inbubble sensor openings653a,653bofbase unit chassis640 detect these conditions and send appropriate signals to the microcontroller to warn a user of when either or both conditions exist.

In an exemplary embodiment, bubble sensor BS1, shown inFIG. 5, ofhumidification system100 detects the rate at which air bubbles are formed inliquid reservoir32 offluid pathway module120. If the bubble formation rate rises above a predetermined level, an auditory warning may be generated and vapor transferdevice fault icon112c, shown inFIG. 13, may illuminate ondisplay panel105 to indicate thatvapor transfer device99 should be replaced with a new cartridge. Alternatively, second bubble sensor BS2 detects the rate at which liquid droplets form in the gas passage ofvapor transfer device99. If the droplet formation rate exceeds a predetermined level, the gas metering and warming operations ofhumidification system100 may be suspended. An auditory warning may be generated andfluid pathway module120icon115, shown inFIG. 13, may illuminate ondisplay panel105, shown inFIG. 13, to indicate thatfluid pathway module120 should be replaced.

FIG. 8D illustrates a side view ofbase unit chassis640 in which electronic reader CS1, CS2, temperatures sensors IR1, IR2, bubble sensors BS1, BS2, and heater HTR2 may be installed. As described above,electronic reader opening657 is configured to receive electronic reader CS1, CS2 which may be installed onbase unit chassis640 via threadedinserts658a,658b.Temperature sensor openings652a,652bare each configured to receive temperature sensor IR1, IR2, which may be mounted tobase unit chassis640 via threaded inserts659a,659band bubble sensors BS1, BS2 may be mounted tobubble sensor openings653a,653bvia threaded inserts661a-c. Heater HTR2 such as a heat conduction plate may be mounted to the heat conduction plate opening651 via threaded inserts663a-d. A side panel (not shown) may be fitted over therear edge664 ofbase unit chassis640 to restrict access to the electrical connections of electronic components, such as readers CS1, CS2, bubble sensors BS1, BS2 (FIG. 5), temperature sensors IR1, IR2, and heater HTR1, which are all shown schematically inFIG. 5.

FIG. 8E illustrates a cross-sectional view ofbase unit chassis640 along the8E-8E line shown inFIG. 8D. As shown inFIG. 8E,base unit chassis640 includes a recessedportion648 configured to receive a gas receiving portion offluid pathway module120.Gas outlet649 of recessedportion648 is configured to receive a gas inlet offluid pathway module120 to supply gas into the gas passage offluid pathway module120. Waterlevel sensor openings654a,654bare disposed along the top and bottom of thecomponent receiving portion619 and are configured to receive water level sensors LS1, LS2 to detect water level influid pathway module120. Guide644aextends from the side of thecomponent receiving portion619 to align and securefluid pathway module120 tobase unit110.

FIG. 8F illustrates a top view ofbase unit chassis640. As described above,base unit chassis640 includes acomponent receiving portion619 having aseat645 that is configured to seatfluid pathway module120. Aseat opening646 is provided to receive pump portion STA1 ofbase unit110 which may be secured tobase unit110 via threaded inserts647a-c.Guides644a,644bextend from the side of thecomponent receiving portion619 to align and securefluid pathway module120 tobase unit110. A recessedportion648 ofbase unit chassis640 includes agas outlet649 which receives gas inlet offluid pathway module120.Opening651 is positioned onbase unit chassis640 to receive heater HTR2.

Referring now toFIG. 9, apump portion96 ofbase unit110 is illustrated.Pump portion96 is configured to mount toseat opening646, shown inFIG. 8A, ofbase unit chassis640 via openings97a-donpump portion96.Installation bracket99 facilitates alignment and installation ofpump portion96.Pump portion96, such as stator STA1 shown inFIG. 5, is configured to operationally mate with pump portion PMP1 offluid pathway module120 to advance liquid through the liquid passage offluid pathway module120. In an exemplary embodiment, pump portion PMP1 offluid pathway module120 is arotatable impeller98 that magnetically couples to pumpportion96. Whenimpeller98 is operationally mated withpump portion96, rotation ofimpeller98 drives the rotation of pump portion PMP1, thereby increasing pressure and liquid flow withinfluid pathway module120.

Fluid Pathway Module (Vapor Transfer Unit)

Referring now toFIGS. 3A, 3B, 10A and 10B, an exemplary embodiment offluid pathway module120 shown inFIG. 3 is illustrated.Fluid pathway module120 is configured to be releasably mounted tobase unit110 to accommodate reuse ofbase unit110 and selective disposal offluid pathway module120.

Referring toFIGS. 3A, 5, and 10A, features and sensors offluid pathway module120 are discussed.Fluid pathway module120 includes handle121 that may be used to insert and removefluid pathway module120 frombase unit110. Whenfluid pathway module120 is mounted tobase unit110, heater HTR1 contacts heater HTR2. Pump portion STA1 ofbase unit110 engages pump portion PMP1 offluid pathway module120. As shown inFIG. 10A,fluid pathway module120 includesliquid inlet124 andgas outlet125.Liquid inlet124 receives liquid fromsupply line75 andgas outlet125 delivers heated and humidified breathing gas to a patient viadelivery tube85.

When liquid (such as water) is supplied toliquid inlet124, liquid is stored withinreservoir32 offluid pathway module120. Asight glass126 on the side offluid pathway module120 provides visual indication of liquid amount inreservoir32 via aplastic ball127 floating withinreservoir32. Tworeflectors128a,128bare visible through thesight glass126 and are positioned to align with water level sensors LS1, LS2. Water level sensors LS1, LS2 ofbase unit110 optically sense water level influid pathway module120 by monitoring light reflection offreflectors128a,128b. For example, whenreservoir32 is full, light reflection fromreflector128ais blocked byplastic ball127 and the humidification system microcontroller (not shown) determines that water level influid pathway module120 is full. Whenreservoir32 is empty, light reflection fromreflector128bis blocked byplastic ball127 andhumidification system100 may cease operation until water is added. If light is reflected from bothreflectors128a,128b,plastic ball127 is floating betweenreflectors128a,128band microcontroller (not shown) may illuminate alow water icon116, shown inFIG. 13, ondisplay panel105, shown inFIG. 3, ofbase unit110 to indicate a low water condition.

Referring toFIGS. 5, and 10B, features and sensors offluid pathway module120 are discussed.FIG. 10B illustrates a side view offluid pathway module120.Fluid pathway module120 includes heater HTR1 in the form ofheat conduction plate122 that heats liquid stored influid pathway module120 by receiving thermal energy from heater HTR1. Adjacentheat conduction plate122 are twotemperature reflectors129a,129bthat are positioned to align with two infrared temperature sensors IR1, IR2. In an exemplary embodiment, temperature sensor IR1, aligned withtemperature reflector129a, monitors the temperature of liquid heated byheat conduction plate122 and temperature sensor IR2, aligned with temperature sensor reflector129b, monitors the temperature of liquid returning tofluid pathway module120 fromdelivery tube85.

Fluid pathway module120 includesgas inlet130 which is configured to receive gas frombase unit110. Whenfluid pathway module120 is mounted tobase unit110, as shown inFIG. 3, an air tight seal is formed betweengas inlet130 andgas outlet649 ofbase unit chassis640, shown inFIG. 8C. As shown inFIGS. 5 and 10B, gas received throughgas inlet130 and liquid stored inreservoir32 flow through passages withinfluid pathway module120 intovapor transfer device99.Vapor transfer device99 is mounted tofluid pathway module120 to form a vapor transfer assembly.Vapor transfer device99 combines water vapor and gas received fromfluid pathway module120 to form heated and humidified breathing gas. Heated and humidified breathing gas flows fromvapor transfer device99 throughoutlet125, shown inFIG. 10A offluid pathway module120, and to the patient viadelivery tube85. Exemplary embodiments of vapor transfer devices that may be used with the present invention are disclosed in U.S. patent application Ser. Nos. 11/851,713, and 10/810,768, which are both incorporated by reference herein in their entireties.

Indicator194, such as a barcode or sticker, is positioned onvapor transfer device99 such that whenvapor transfer device99 is coupled tofluid pathway module120 and mounted on base unit110 (FIG. 3), an electronic reader CS1, CS2 aligns withindicator194. Thus, the type ofvapor transfer device99 installed onfluid pathway module120 such as a low flow or high flow cartridge, described above, may be determined by a microcontroller (not shown) ofhumidification system100.

During operation ofhumidification system100, the internal core ofvapor transfer device99 may degrade, resulting in the mixing of gas and water vapor within vapor transfer device199 becoming less efficient. In this instance, gas pockets may enter the liquid passage offluid pathway module120 so that air bubbles form inliquid reservoir32. In another instance, droplets of liquid may enter the gas passage. These conditions are monitored by bubble sensors BS1, BS2. Bubble sensors BS1, BS2 align withbubble reflectors131a,131bonfluid pathway module120. In an exemplary embodiment, bubble sensor BS1 aligned withbubble reflector131amonitors air bubble formation withinliquid reservoir32 and bubble sensor BS2 aligned withbubble reflector131bmonitors liquid droplets in the gas passage. When the rate at which air bubbles or liquid droplets are detected exceed predefined detection rates, signals may be sent to humidification system microcontroller to generate auditory warnings and illuminatefault icons115,112condisplay panel105, shown inFIG. 13, to warn a user of these conditions. Additional aspects of warnings and fault icons will be described in further detail below.

FIGS. 11A and 11B illustrate exploded views of a portion offluid pathway module120 shown inFIGS. 10A and 10B. As shown inFIG. 11A,main body120aoffluid pathway module120 includesliquid reservoir32 to store liquid received throughliquid inlet124. A waterlevel sensor plate133 havingupper reflector128aandlower reflector128bis configured to be positioned within thereservoir32 and is visible throughsight glass126. Anon-reflective level ball127 is configured to be positioned within thereservoir32 such that it floats withinreservoir32 as previously described. Optical water level sensors LS1, LS2 monitor the light reflection fromreflectors128a,128b, thereby determining the water level withinreservoir32.

Main body120aoffluid pathway module120 includes heater HTR1 in the form of a heat conduction plate. Throughoutdevice100, heat is transferred from heater HTR2, located inbase unit110, to heater HTR1, located influid pathway module120, via conduction. Heat is then transferred by conduction from heater HTR1 to liquid inreservoir32 whenfluid pathway module120 is mounted tobase unit110. A temperature andbubble sensor plate135 isadjacent heater portion134 and is configured to couple withtemperature reflectors129a,129bandbubble reflectors131a,131b.

As shown inFIG. 11B, temperature andbubble sensor plate135 is configured to fit overtemperature reflector portions129a,129bandbubble reflector portions131a,131b.Main body120aincludeshandle121 which may be used to insert or removefluid pathway module120 frombase unit110. Tubular support structures136a-eextend from the side ofmain body120a. Tubular support structures136a-eare configured to mate with vaportransfer device adapter120b, shown inFIG. 12. In an exemplary embodiment,vapor transfer device99 is configured to couple to support structures136a-csuch that passages defined by support structures136a-cconnect with passages ofvapor transfer device99. Liquid and gas may be exchanged through the passages to generate heated and humidified breathing gas invapor transfer device99. Heated and humidified breathing gas, for example, may be supplied togas outlet125 offluid pathway module120, shown inFIG. 10A, through the passage defined bysupport structure136a. In an exemplary embodiment, heated liquid may be supplied tovapor transfer device99 through the passage defined bysupport structure136cand recycled through the passage defined by support structure136b.

Referring now toFIGS. 11A and 12, vaportransfer device adapter120bis configured to couple tomain body120ato fully assemblefluid pathway module120. Vaportransfer device adapter120bincludes passages137a-ethat are configured to mate with support structures136a-eofmain body120a.

Referring now also toFIGS. 10A and 10B, vaportransfer device adapter120bincludes gas inlet portion130aconfigured to mate with reciprocalgas inlet portion130bto formgas inlet130.Gas inlet130 receives gas frombase unit110 and channels gas togas opening138.Gas opening138 is configured to connect to a gas passage ofvapor transfer device99 and supply gas intovapor transfer device99. Gas fromgas opening138 and heated water frompassage137care used invapor transfer device99 to generate heated and humidified breathing gas. In an exemplary embodiment, heated and humidified breathing gas exitsvapor transfer device99 through passage137aand is delivered to breathinggas outlet125 offluid pathway module120. As further shown inFIGS. 5 and 12, excess water invapor transfer device99 frompassage137cis recycled back intoliquid reservoir32 throughpassage137b.

In an exemplary embodiment,gas inlet130 includes an air port ball139athat is configured to be contained withincap130b. An O-ring139cis positioned at a distal end ofcap139band provides a circumferential seal around a distal opening of thecap139b.Cap cover139dis positioned distally from O-ring139cand is configured to seat O-ring139cwhencap cover139dis secured around a portion ofcap139b. In an embodiment of the present invention, whengas inlet portions130a,130bare mated together and coupled to cap139bandcap cover139d, the air port ball130amoves freely between O-ring139canddistal opening193a,193bofgas inlet portions130a,130b. In one embodiment, gas flow intogas inlet130 causes air port ball139ato move in a direction opposing gravity. When gas flow throughgas inlet130 exceeds gravitational pull on air port ball139a, air port ball139awill “float”. In another embodiment, when gas is not supplied togas inlet130, air port ball130awill contact and seal O-ring139cto prevent air flow into gas outlet649 (FIG. 8C) of base unit chassis640 (FIG. 8C). Under normal operating conditions, air port ball239awill “float” betweendistal opening193a,193band O-ring139c, thereby providing gas flow throughgas opening138. Thus, as shown inFIGS. 1 and 5, gas only flows in one direction frombase unit110 intofluid pathway module120.

Referring now toFIG. 10B andFIG. 12, aflexible lip139eis positioned betweengas inlet portions130a,130bandadjacent gas opening138. In one embodiment, whenvapor transfer device99 is coupled tofluid pathway module120,lip139eis deformably opened such that gas may flow intovapor transfer device99. Whenvapor transfer device99 is removed fromfluid pathway module120,lip139eis deformably sealed to prevent air from flowing in a direction fromgas opening138 into thegas outlet130.

Operation and Display

Referring now toFIGS. 13 and 14, exemplary aspects of operational modes, warning indicators and a flow chart of the operation of humidification system is100 are illustrated.Vapor transfer device99 is releasably mounted tofluid pathway module120 such that liquid and gas communication is provided betweenvapor transfer device99 and fluid pathway module120 (STEP510).Fluid pathway module120 is releasably mounted tobase unit110 such thatbreathing gas50a,50bsupplied intobase unit110 flows intofluid pathway module120 and through vapor transfer device99 (STEP520). Breathinggases50a,50bare blended inside agas blending device84 to form a blended gas60 (STEP530). Thermal energy is transferred frombase unit110 tofluid pathway module120, thereby heatingliquid70 in a liquid passage of fluid pathway module120 (STEP540).Liquid70 is heated influid pathway module120 and is used to heat and humidify blendedgas60 and maintain a desired temperature of breathing gas80 (STEP550).Heated liquid70 and blendedgas60 are passed throughvapor transfer device99, thereby forming heated and humidifiedbreathing gas80, which is then delivered to a patient (STEP560), e.g., via a nasal cannula (not shown).

Front panel104 ofbase unit110 includesdisplay panel105 that provides visual indication of the operating conditions ofhumidification system100. In an exemplary embodiment, when AC power is supplied tohumidification system100 throughelectrical cord65,battery icon113 may illuminate ondisplay panel105 to indicate that an internal battery (not shown) is charging.Battery icon113 may flash to indicate that the battery backup time is reduced in the event that AC power is lost during charging. When the battery is fully charged,battery icon113 automatically switches off.

Whenhumidification system100 is powered on andelectrical cord65 is disconnected frombase unit110,battery icon113 may illuminate to indicate that DC power is being used. When a loss of AC power occurs in RUN mode,system100 automatically enters BATTERY mode. In BATTERY mode, heater HTR2 and pump stator STA1 are turned off to conserve battery power. Gas flow control and delivery continues unabated. When AC power is reestablished,system100 automatically returns to RUN mode. In BATTERY mode, pressing the Run button causessystem100 to enter POWER_OFF mode. If battery capacity is exhausted,system100 will enter POWER OFF mode.

Whenhumidification system100 is powered off, pressing the “Standby/Run”button108bactivates an initial boot-up stage that performs a series of self-tests to verify the proper function of subsystems, sensors, and actuators contained inbase unit110. During system boot-up, if any self-test diagnosis fails, asystem fault icon114 is illuminated ondisplay panel105, and operation ofhumidification system100 is disabled. If all self-tests pass,humidification system100 transitions to “standby” mode and sensors inbase unit110 are activated to detect the presence offluid pathway module120 inbase unit110. Iffluid pathway module120 is not detected onbase unit110 or if bubble sensors BS1, BS2 detect thatfluid pathway module120 needs to be replaced, fluid pathwaymodule fault icon115 is illuminated. In an embodiment of the present invention, whenfluid pathway module120 is mounted tobase unit110, fluid pathwaymodule fault icon115 is switched off and water level sensors LS1, LS2 inbase unit110 are activated to detect water level influid pathway module120. If the water level is low, alow water icon116 flashes on/off and an audible alarm sounds to indicate thatreservoir32 offluid pathway module120 should be refilled by providing additional water throughwater supply line75. If the water is empty,low water icon116 in constantly illuminated an audible alarm sounds.

Whenfluid pathway module120 is mounted tobase unit110, an electronic reader CS1, CS2 is activated to detect the presence ofvapor transfer device99. Ifvapor transfer device99 is not detected onfluid pathway module120 or if bubble sensors BS1, BS2 detect thatvapor transfer device99 is worn, vapor transferdevice fault icon112cis illuminated. In an exemplary embodiment, whenvapor transfer device99 is coupled tofluid pathway module120 and installed inbase unit110, the type ofvapor transfer device99 installed is determined by electronic reader CS1, CS2. For example, if a high flowvapor transfer device99 is detected, a high flow icon212ais illuminated on thedisplay panel105. If a low flow vapor transfer device is detected99, alow flow icon112bis illuminated. In yet another embodiment, detection offluid pathway module120 andvapor transfer device99 is performed concurrently such that whenvapor transfer device99 is detected, the system automatically determines thatfluid pathway module120 is installed onbase unit110.

Gas flow to the patient is a metered blending of the two input gases, such as medical air and oxygen. A closed feedback control loop exists between the proportional solenoids PSOL1, PSOL2 that control the flow of each gas, and mass flow MFS1, MFS2 sensors that measure the gas flow.

A gas blending algorithm controls the gas blending process. A gas blending algorithm suitable to control the gas blending process will be understood by one having ordinary skill in the art from the description herein. Mass flow sensors MFS1, MFS2 measure the flow rates of medical air and oxygen gases. Proportional solenoids PSOL1, PSOL2 control the flow rates of the gases. Each valve PSOL1, PSOL2 is controlled by a digital to analog converter (DAC), not shown.

A non-linear relationship exists between the output of gas flow sensors MFS1, MFS2 and the corresponding representation in engineering units, such as Standard Liters Per Minute (SLPM). In order to maximize the accuracy of operation and to compensate for part tolerances, a suitable lookup table is provided in the system microprocessor to implement a non-linear transformation function. In one embodiment, the lookup table includes201 entries that are defined for each of mass flow sensors MFS1, MFS2. The lookup table is indexed by engineering units in 0.25 SLPM increments, and returns values corresponding to the output of mass-flow sensors MFS1, MFS2 in raw 12-bit A/D counts. Fractional indices may be resolved through linear interpolation between table entries.

Whensystem100 is configured for single gas operation,oxygen saturation level106cis set for 21% for air and 100% for oxygen. An audible alarm sounds if the user attempts to edit or otherwise adjust the value foroxygen saturation level106c. To select single gas operation, the user attaches an air or an oxygen supply to one ofgas inlet ports101a,101bwhilesystem100 is in standby mode.

To select dual gas operation, the user attaches gas supply lines to each ofgas inlet ports101a,101bwhilesystem100 is in standby mode. If either gas supply loses pressure whilesystem100 is in dual gas operation, an audible alarm sounds.

It is further contemplated that when anyhumidification system100 fault condition exists, auditory warning alarms may be generated. For example, auditory tones and alarms may be generated concurrently when warning indicators are displayed ondisplay panel105. In another embodiment, alarms may be programmed with unique auditory patterns depending of the priority of the warning. For example, a low priority auditory warning may sound briefly to indicate the occurrence of an event that does not require immediate user attention, whereas a higher priority auditory warning may sound continuously to indicate that immediate attention is required.

Warning alarms may be muted by pressing themute button108aof theuser interface107. In one embodiment, pressing themute button108ailluminates LED109ato provide visual indication that warning alarms are muted. In another embodiment, pressingalarm button108amutes low priority auditory warnings, while higher priority auditory warnings may remain auditory. In yet another embodiment,alarm button108afunction may be programmed with additional user adjustable settings such as controlling the brightness ofdisplay panel105. For example, pressingalarm button108afor a period of time may adjust the brightness ofdisplay panel105.

Whenhumidification system100 is in “standby” mode, user settings such as thetemperature106a,flow rate106b, andoxygen saturation level106cof the breathing gas may be adjusted usingencoder knob111 ofuser interface107. In exemplary embodiment, pressingencoder knob111 cycles through user settings that can be adjusted. Pressing theencoder knob111 once, for example, may activate the temperature adjustment setting andpressing encoder knob111 in succession may cycle through additional user settings that can be adjusted. In an exemplary embodiment, pressingencoder knob111 causes the user setting that is activated to blink ondisplay panel105, thus indicating the specific user setting that may be adjusted. In an exemplary embodiment, rotatingencoder knob111 while in an activated user setting allows the current user setting setpoint to be adjusted. For example, clockwise rotation ofencoder knob111 may increase the setpoint androtating knob111 counterclockwise may decrease the setpoint. In another embodiment,encoder knob111 has an acceleration feature, in whichturning knob111 faster causes the setpoint to increase or decrease in larger steps.

According to one embodiment, after the desired user setting has been set, pressing “Standby/Run”button108btransitions humidification system from “standby” mode to “run” mode. When the system is in “run” mode,status LED109bmay be illuminated to indicate that the gas metering and heating operations of the system are activated to deliver heated and humidified gas to the patient.Base unit110 includes gas pressure sensors to detect if the breathinggas delivery tube85 is blocked and if gas supply intobase unit110 is too low or too high. Atube fault icon117 may be lit ondisplay panel105 when base unit senses a pressure indicating that the breathinggas delivery tube85 is kinked or blocked. Gassupply fault icon118 may be displayed when a gas supply problem, such as low or high gas pressure is input tohumidification system100.

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

Claims (29)

What is claimed:

1. A system controlled by a microcontroller for delivering heated and humidified breathing gas to a patient through a nasal cannula, comprising

a base unit, a vapor transfer assembly, and a breathing gas conduit extending from the vapor transfer assembly;

the base unit comprising:

a heater,

a gas flow sensor,

a gas blending device having first and second gas supply lines, and a gas outlet conduit,

the first gas supply line comprising a first supply conduit with proximal and distal ends, its proximal end being operable to receive air from an air source,

the second gas supply line comprising a second supply conduit with proximal and distal ends, its proximal end being operable to receive oxygen from an oxygen gas source, and

the gas outlet conduit being configured to receive gas from the first supply conduit and air from the second supply conduit and expel blended gas to the vapor transfer assembly; and

the vapor transfer assembly comprising:

a disposable fluid pathway module having a housing releasably mounted to the base unit, a reservoir for containing liquid, and a gas inlet configured to receive flowing gas from the gas outlet conduit,

a heating plate positioned in the housing so as to receive heat from the heater and produce heated vapor from liquid contained in the reservoir when the housing is mounted to the base unit and the heater is actuated, and

a cylindrical vapor transfer device coupled to the disposable fluid pathway module and being configured with a passage to receive blended gas from the gas inlet and configured to combine the blended gas with the heated vapor to provide heated and humidified breathing gas through the breathing gas conduit.

2. The system ofclaim 1, wherein the disposable fluid pathway module further comprises a main body having a plurality of sides and a support structure extending from at least one of the plurality of sides, the support structure being configured to couple to the vapor transfer device to create a connecting passage through which gas can flow into the vapor transfer device.

3. The system ofclaim 2, wherein the disposable fluid pathway module includes an adapter with an adapter passage configured to mate with the support structure to form the connecting passage.

4. The system ofclaim 3, wherein the vapor transfer device has an upper portion, a lower portion, and a side wall extending between the upper and lower portions, and wherein the upper portion is releasably mated to the adapter.

5. The system ofclaim 3, wherein the adapter has a first inlet portion configured to mate reciprocally with a second inlet portion to form an inlet channel for channeling gas into the vapor transfer device.

6. The system ofclaim 3, wherein the support structure defines a passage positioned between the vapor transfer device and the reservoir so that heated liquid from the reservoir may flow through the passage into the vapor transfer device.

7. The system ofclaim 6, configured so that heated and humidified breathing gas exits the vapor transfer device through a passage in the adapter and is delivered to the breathing gas outlet of disposable fluid pathway module.

8. The system ofclaim 7, wherein excess water in the vapor transfer device is recycled back into the reservoir through a passage in the adapter.

9. The system ofclaim 3, wherein the gas blending device includes a blending channel attached to the respective distal ends of the first and second gas supply conduits and to the proximal end of the outlet conduit.

10. The system ofclaim 9, wherein the first and second gas supply conduits have respective first and second cross sectional diameters, and the blending channel has a third cross sectional diameter that is larger than either of the first and second cross sectional diameters.

11. The system ofclaim 9, wherein the gas blending device has first and second body portions joined by adhesive, each body portion having at least four complementary channels, and wherein each complimentary channel on one of the first and second body portions is configured to mate with a respective complimentary channel on the other of the first and second body portions, such that when the first and second body portions are joined together, flow passages are formed by the mated complementary channels to create the first and second gas supply conduits, the blending channel, and the outlet conduit.

12. The system ofclaim 11, wherein complementary channels forming the first gas supply conduit are positioned in the base unit so as to extend generally in parallel with complementary channels forming the second gas supply conduit.

13. The system ofclaim 11, comprising at least one fin positioned within at least one of the first and second supply conduits and output conduit.

14. The system ofclaim 13, comprising a plurality of projections that form a tortuous path within the gas outlet conduit.

15. The system ofclaim 11, comprising first and second valves positioned between, respectively, the first channel and first gas supply line, and between the second channel and second gas supply line.

16. The system ofclaim 15, wherein the first channel is operable to receive the medical air when the first valve is open and flow the medical air into the gas blending device, and the second channel is operable to receive the oxygen when the second valve is open and flow the oxygen into the gas blending device.

17. The system ofclaim 3, wherein the gas flow sensor includes an oxygen flow rate sensor and an air flow rate sensor.

18. The system ofclaim 17, wherein the microcontroller is configured to receive inputs indicative of oxygen and air flow rates and adjust at least one of the flow rate of the air and the flow rate of the oxygen into the base unit.

19. The system ofclaim 18, comprising an oxygen saturation sensor.

20. The system ofclaim 19, wherein the microcontroller is further configured to receive a sensor input from the oxygen saturation sensor and adjust the flow rate of oxygen into the base unit.

21. The system ofclaim 20, wherein the microcontroller controls the flow rate of oxygen into the mixing chamber by opening a valve when the oxygen saturation sensor input is below a threshold.

22. The system ofclaim 3, further comprising a docking sensor configured to detect the coupling of the disposable fluid pathway module to the base unit.

23. The system ofclaim 22, wherein the docking sensor includes an indicator on the vapor transfer device.

24. The system ofclaim 23, wherein the docking sensor is configured to read a bar code on the disposable fluid pathway module or has an optical sensor.

25. The system ofclaim 24, comprising a releasable door positioned on the base unit for interfacing with the housing and locking the disposable fluid pathway module to the base unit.

26. The system ofclaim 25, wherein closing the door completely encloses the disposable fluid pathway module within the base unit.

27. The system ofclaim 26, comprising a pump having an actuation interface within the base unit and configured to circulate fluid from the reservoir into the vapor transfer device.

28. The system ofclaim 3, comprising a nasal cannula operably positioned to receive breathing gas from the disposable fluid pathway module.

29. The system ofclaim 3, further comprising a compressor that interfaces with an air source for delivering medical air into the first conduit.

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